1. Field of the Invention
The present invention relates to movable body methods and apparatuses, exposure methods and apparatuses, pattern formation methods and apparatuses, and device manufacturing methods, and more particularly to a movable body drive method and a movable body drive apparatus that drive a movable body along a predetermined plane, an exposure method that makes use of the movable body drive method and an exposure apparatus equipped with the movable body drive apparatus, a pattern formation method that makes use of the movable body drive method and a pattern formation apparatus equipped with the movable body drive apparatus, and a device manufacturing method that makes use of the pattern formation method.
2. Description of the Background Art
In a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (integrated circuits and the like) and liquid crystal display devices, an exposure apparatus such as a reduction projection exposure apparatus by a step-and-repeat method (a so-called stepper) or a reduction projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner)) is mainly used.
In this type of exposure apparatus, in order to transfer a pattern of a reticle (or a mask) to a plurality of shot areas on a substrate such as a wafer or a glass plate (hereinafter, generically referred to as a wafer), a wafer stage that holds a wafer is driven in two-dimensional directions with, for example, a linear motor or the like. The position of the wafer stage was generally measured using a laser interferometer that has high stability for over a long period.
In recent years, however, requirements for overlay accuracy are increasing due to finer patterns that accompany higher integration of semiconductor devices, and now, short-term variation of measurement values caused by air fluctuations generated due to temperature change or temperature gradient of the atmosphere in the beam path of the laser interferometer has come to occupy a large percentage in the overlay budget.
Therefore, the inventor proposed before, an exposure apparatus that employs an encoder that has a measurement resolution of a level same as or higher than that of a laser interferometer and is less affected by air fluctuations compared with an interferometer in general, as a position measuring device of a wafer stage (e.g. refer to the pamphlet of International Publication No. 2007/097379). As a result of the inventor and the like performing various experiments, recently it has been found that if a measurement beam continues to be irradiated to a scale in which a diffraction grating is formed for over a given period of time or more, the scale minutely deforms due to thermal expansion and this minute deformation can be a factor of measurement error of a level that cannot be ignored.